Auto Power Environment

[Eric Bryant]

> From: Mike Turner/ENGR/HQ/KEMET/US [mailto:MikeTurner at kemet.com]
> Subject: Auto Power Environment
> 
> Some time ago, there was a discussion of the theoretical 
> 12vdc automotive
> power environment such as reversed battery, battery jump 
> start, cranking,
> etc.

Each manufacturer is a bit different, but here's the range of conditions
that I've seen:

Operating voltage: 9-16 V (upper limits vary depending on OEM customer)

Reversed battery: -16 V for one minute

Boosted jump start: 26 V for one minute

Overvoltage: 20 V for one hour

Cranking: 6 V continuous during crank, 4 V for 500 ms, 0 V for 15 ms

Load Dump: 130 V for 100 ms (side note: VW/Audi does not appear to have a
universal load dump requirement, so apparently they don't suffer from
battery terminal corrosion:) ).

You might also see a "superimposed AC voltage" requirement, where a sawtooth
wave is superimposed on the DC supply.  VW/Audi calls for a sweep from 50 Hz
to 20 kHz and back within 1 minute, and the test is performed for 5 minutes
(5 complete sweeps of frequency).  It's a 2 V sawtooth on a 12 V supply.
I'm not sure if any of the other OEMs require something similar; it's been a
while since I've looked into them closely. 

There's a variety of temperature ranges for these tests, too.  You'll
usually see a requirement for operation at 9-16 V under any temperature
condition, but the boosted jump start test might only be done at room temp.


I'm sure I'm forgetting some, but these should be enough to get the gears
turning.  There's a lot of variation from OEM to OEM, so it can be kinda
difficult to compile a "generalized" list.  If someone was ambitious enough,
they could create a "super spec" by combining the worst of all the specs
available.  It'd be a bit of overkill, but you'd have a very stout test
procedure by the time it's done.


Eric Bryant
mailto:bryante at ghsp.com
http://www.novagate.com/~bryante 
 
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